I think it was probably an add-on to the fact that in Best Wishes, he got more visible eyes.

Now, after seeing the opening titles that was leaked a few days back it apparently shows this saga may pull a Hoenn on us as far as starter distribution with the main characters goes. Clemont was shown alongside Chespin, Serena was shown with Fennekin and Ash with Froakie.

If this was the case, it means they'd finally have broken the long trend of Ash getting the Grass starter. I always thought Froakie suited him better, so if Ash only gets Froakie it would definitely make room for diversity in his team like how it was in Hoenn. Also, Froakie better evolve. Ash needs a fully-evolved Water starter and Greninja would suit him perfectly! Even if they left him as a Frogadier I'd be fine because they'd finally make Ash's Water starter evolve.